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In order to alleviate the increasingly severe climate warming problem, countries are actively promoting low-carbon economic transformation. Cultivated land use activities have dual effects of carbon emission and carbon absorption. An in-depth analysis of China’s net carbon source/sink of cultivated land use and its relationship with grain yield can provide decision-making references for ensuring food security and achieving China's "30.60 dual carbon" goal. Taking China's 31 provinces as the research unit, the net carbon sink of cultivated land use between 1991 and 2021 was calculated, the driving factors of carbon emission from cultivated land use were analyzed, the spatial-temporal characteristics of carbon emission and net carbon sink were pictured, and the improved Tapio coupling index was used to explore the relationship between the net carbon sink of cultivated land use and grain yield. The results showed that: (1) The carbon emission of cultivated land use showed an upward first and then downward trend, reaching a peak of 81.0579 million tons in 2015. Among the factors influencing carbon emissions of cultivated land use, the efficiency and economic factors have the most significant positive and negative effects on the carbon emission reduction of cultivated land use, respectively. (2) In the past 31 years, the net carbon sink of cultivated land use has increased from 404.595 million tons to 666.848 million tons, and China's cultivated land use system has always been in a state of carbon sinks. (3) At the national level, the net carbon sink of cultivated land use and grain yield are growth coupling or yield-dominant coupling in most years. The types of coupling at the regional level are varied but still dominated by growth coupling. Typically, provinces have a balanced relationship between the increased net carbon sink of cultivated land use and the increase in grain yield. Accordingly, the transformation of cultivated land use should be accelerated, the industrial structure of the plantation industry should be optimized, reasonable cultivated land protection policies should be formulated, and the reduction of carbon sources and increase of carbon sinks in large emitting provinces should be promoted by classification and batch.

Opponents of migration argue that natives bear the fiscal costs of immigration. Estimates suggest the longrun fiscal effect of immigration for local governments is negative, largely due to the costs of educating immigrant children. We test whether migration affects local government fiscal outcomes using a synthetic control method and the 1980 Mariel Boatlift as a natural experiment. We find no effect of the mass influx of migrants to Miami on various fiscal outcome measures, suggesting concerns over the fiscal effects of immigration are "missing the boat."